The present invention relates to an improved nozzle design for use in a cold spray system for depositing metal alloy coatings onto a workpiece.
Cold gas dynamic spraying (e.g. cold spray) is a relatively new technology where powder metal is deposited through solid state bonding. This bonding mechanism is achieved through acceleration of the particles to supersonic speeds through a converging/diverging (Laval) nozzle using helium and/or nitrogen gas. U.S. Pat. No. 5,302,414 to Alkhimov et al., which is hereby incorporated by reference herein, illustrates a cold gas dynamic spraying system.
Typical nozzle materials which have been used in cold spray systems include brass, stainless steel, and tool steel. During deposition of certain materials, namely aluminum and some nickel alloys, the nozzle will foul or clog with the metallic powder causing system failure and rework to remove the damaged nozzle. Fouling of aluminum occurs within a matter of 3-4 minutes, whereas a minimum of 8 hours continuous operation is desired to commercialize this new technology.